Pellet handling apparatus and fuel rod loading method

ABSTRACT

A pellet magazine includes a plurality of pellet bores sized to receive pellets for loading into a fuel rod. A fuel rod loading system includes a plurality of pellet loading stations each designated to load a single pellet type into one or more pellet bores of the pellet magazine, a rod loading station configured to unload pellets from the pellet bores of the pellet magazine into a fuel rod, and a conveyance system configured to transport the pellet magazine to the loading stations and then to the rod loading station in a defined sequence.

CLAIM OF PRIORITY

This application is a Division of U.S. patent application Ser. No.14/207,995 filed on Mar. 13, 2014, now U.S. Pat. No. 10,720,252, whichclaims the benefit of U.S. Provisional Application No. 61/783,671 filedMar. 14, 2013, the disclosures of which are hereby incorporated byreference in their entirety.

BACKGROUND

The following relates to the nuclear reactor fuel handling arts, nuclearfuel rod loading arts, nuclear fuel pellet handling arts, and relatedarts.

The nuclear reactor core of a nuclear reactor is typically assembled asa set of fuel rods. Each fuel rod comprises a hollow cylindricalcladding filled with fuel pellets (and/or possibly pellets of othertypes, such as spacer pellets, and/or pellets containing a neutronpoison) and capped by end plugs. The composition, enrichment, andarrangement of the pellets loaded into a given fuel rod are chosen toprovide designed reactivity or other characteristics. For example, oneillustrative reactor core design includes fuel rods comprising uraniumdioxide (UO₂) of various enrichment levels, and spike fuel rodscomprising UO₂Gd₂O₃ for reactivity control. The enrichment (i.e. fissile²³⁵U concentration or fraction) of fuel pellets may be varied over thelength of the fuel rod and/or among different fuel rod types. Typically,the pellets loaded into a given fuel rod are arranged as discrete axialzones along the length of the fuel rod, with each zone having a definednumber of fuel pellets of the same defined composition and ²³⁵Uenrichment. The loading of the fuel pellets into the fuel rods must bedone with exacting precision so that the assembled nuclear reactor corehas the designed characteristics. Regulatory rules and best practicesdictate that the fuel loading be documented and traceable so that thecomposition of each fuel rod is known and traceable throughout themanufacturing, shipping, and reactor fueling processes.

In so-called vibratory pellet loading methods, multiple pieces of emptyfuel rods (with welded lower end plug) are placed on a large vibratorytable. The upper ends of the rods fit within a transition element. Thetransition element guides the pellets from a v-trough into the rods.Pellets are arranged in the v-trough in the correct length in front ofeach transition. The table is then excited (i.e. vibrated) such that thepellets move under their own inertia into the rods. The process isrepeated until all the segments are loaded.

The handling of large pellet trays is a significant challenge foroperators. The trays must be loaded and unloaded for each enrichmentzone. The loading time increases with the number of zones. Multiple rodsare loaded at the station to minimize cycle time. Pellets of differenttypes for the different axial zones may be arranged in the v-trough,raising the possibility of inadvertent mixing of pellets of differenttypes.

Disclosed herein are improvements that provide various benefits thatwill become apparent to the skilled artisan upon reading the following.

BRIEF SUMMARY

In one disclosed aspect, a system comprises: a pellet magazine having aplurality of pellet bores wherein each pellet bore is open at least atone end and is sized to receive and retain pellets; a plurality ofpellet loading stations wherein each pellet loading station isconfigured to transfer pellets of a single type into one or more pelletbores of the pellet magazine; a rod loading station configured totransfer pellets from the pellet bores of the pellet magazine into anuclear fuel rod; and a conveyance system configured to convey thepellet magazine between the pellet loading stations of the plurality ofpellet loading stations and then to the rod loading station in order totransfer an ordered stack of pellets from the plurality of pelletloading stations into a nuclear fuel rod. In some embodiments the pelletbores of the pellet magazine include longitudinal slots and the rodloading station includes an element configured to pass into thelongitudinal slot and move along the longitudinal slot to push pelletsout of the pellet bore. In some embodiments the conveyance system isconfigured to cooperate with the plurality of pellet loading stations toload the ordered stack of pellets into the pellet magazine as aplurality of ordered stack segments wherein each ordered stack segmentis stored in one of the pellet bores, and the rod loading station isconfigured to transfer the ordered stack segments from the pellet boresof the pellet magazine into a nuclear fuel rod in order to transfer theordered stack of pellets into the nuclear fuel rod. In some suchembodiments, a gamma camera is configured to acquire a gamma radiationimage of the pellet magazine with the ordered stack segments stored inthe pellet bores.

In another disclosed aspect, a pellet magazine is disclosed, having aplurality of pellet bores wherein each pellet bore is open at least atone end and is sized to receive and retain ²³⁵U enriched nuclear fuelpellets. The pellet bores of the pellet magazine may includelongitudinal slots. An apparatus embodiment includes the pellet magazineand ²³⁵U enriched nuclear fuel pellets disposed in at least one pelletbore of the pellet magazine.

In another disclosed aspect, a method is disclosed which uses aplurality of pellet loading stations and a nuclear fuel rod loadingstation. The method comprises: (i) transferring a pellet magazine toeach pellet loading station of the plurality of pellet loading stationsin succession in a predetermined order and, at each pellet loadingstation, loading pellets of a single type into one or more pellet boresof the pellet magazine; and, after operation (i) is complete, unloadingthe pellets from the pellet bores of the pellet magazine into a nuclearfuel rod at the nuclear fuel rod loading station in a predeterminedunloading order so as to transfer an ordered stack of pellets into thenuclear fuel rod. In some embodiments, the operation (ii) includesunloading the pellets from the pellet bores of the pellet magazine intothe nuclear fuel rod by operations including inserting an element into alongitudinal slot extending along a pellet bore of the pellet magazineand moving the inserted element along the longitudinal slot to pushpellets out of the pellet bore. In some embodiments, after completingthe operation (i), a gamma radiation image of the pellet magazine isacquired.

In another disclosed aspect, a system comprises: a pellet magazineincluding a plurality of pellet bores open at least at one end and sizedto receive pellets; and a rod loading station configured to transferpellets from the pellet bores into a fuel rod. The system may furtherinclude a plurality of pellet loading stations each configured to loadpellets of a single type into the pellet bores of the magazine. Thesystem may further include a conveyor belt or other conveyance systemarranged to transfer the pellet magazine between the pellet loadingstations and the rod loading station in a defined sequence.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take form in various components and arrangements ofcomponents, and in various process operations and arrangements ofprocess operations. The drawings are only for purposes of illustratingpreferred embodiments and are not to be construed as limiting theinvention.

FIGS. 1 and 2 diagrammatically shows a bottom view and an end view,respectively, of a pellet magazine as disclosed herein.

FIG. 3 diagrammatically shows an overhead view of an automated pelletloading system employing magazines of the type shown in FIGS. 1 and 2.

FIG. 4 diagrammatically shows the rod loading station of the pelletloading system of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIGS. 1 and 2, bottom and end views, respectively, ofa pellet magazine 10 are shown. The pellet magazine 10 is a platecontaining a plurality of parallel pellet bores 12 (see FIG. 2) sized toreceive pellets to be loaded into the fuel rod. The illustrative pelletmagazine 10 of FIGS. 1 and 2 includes eleven (11) parallel pellet bores12, but a larger or smaller number of pellet bores may be employed.Optionally, the pitch of the magazine bores 12 is the same as the pelletstorage/shipping trays. As seen in the end view of FIG. 2, each pelletbore 12 includes a longitudinal slot 14 running the length of the pelletbore 12 which admits an ejection finger (see FIG. 4) for pushing thepellets out of the pellet bore and into the fuel rod (optionally througha transition element that facilitates coupling of the pellet bore withthe fuel rod). In the illustrative embodiment, the longitudinal slots 14are at the magazine bottom 16 (see FIG. 1), and the magazine top 18 iscontinuous and does not have slot penetrations (see FIG. 2).

With reference to FIG. 3, a diagrammatic overhead view is shown of anautomated pellet loading system 30 employing magazines 10 of the typeshown in FIGS. 1 and 2. To increase throughput, multiple pelletmagazines 10 are contemplated to be used in production, e.g. inillustrative FIG. 3 nine magazines 10 are shown at various points in theloading process. The pellet magazines 10 are preferably identified bybarcodes, RFID tags, or another suitable tracking feature (not shown).The pellet magazines 10 are routed to individual loading stations via apellet loading conveyer belt 32. To minimize the likelihood of mixingpellets of different types, in some embodiments each pellet loadingstation handles pellets of a single type (i.e. a single composition andenrichment level). In the illustrative pellet loading system of FIG. 3,the pellet loading conveyor belt 32 connects with five loading stationsL1, L2, L3, L4, L5 for five different enrichment levels. In someembodiments, it is contemplated for one or more loading stations to bedesignated for loading pellets of a non-fuel type, such as pelletscomprising a neutron poison, or spacer pellets that do not containeither enriched uranium or neutron poison. At each pellet loadingstation, pellets of the type handled by that station are loaded into oneor more of the pellet bores 12 (see FIG. 2) of the magazine 10. Thus, asdiagrammatically indicated in FIG. 3, magazine 101 is empty when itreaches the first loading station L1 (for pellets designated “Enrich1”). In this illustrative example, pellets are loaded into one pelletbore, and then the magazine is transferred by the conveyor belt 32 tothe second loading station L2 (for pellets designated “Enrich 2”). Notethat the designations herein of “Enrich 1”, “Enrich 2”, and so forth arearbitrary designations, and in general the enrichment level of “Enrich1” may be the same as, higher than, or lower than, the enrichment levelof “Enrich 2”, and similarly for other “Enrich-” level designations.Magazine 102 arrives at the second pellet loading station L2, and itssecond pellet bore is loaded with pellets of the “Enrich 2” type andthen the magazine is transferred to the third loading station, arrivingat the third loading station L3 as illustrated magazine 103 for loadingof pellets designated “Enrich 3”. At the third loading station L3 twopellet bores are loaded with “Enrich 3” pellets, and the magazine isthen transferred to the fourth loading station L4 arriving asillustrative magazine 104 for loading of pellets designated “Enrich 4”.At the loading station L4 two more pellet bores are loaded, this timewith “Enrich 4” type pellets. Finally (in the illustrative example),illustrative magazine 105 arrives at the fifth loading station L5, wheretwo more pellet bores are loaded, now with “Enrich 5” type pellets.

In the illustrative example of FIG. 3, each pellet bore 12 is shown asbeing fully loaded over the entire bore length with pellets. However,this is not necessary. For example, if a given axial zone of the fuelrod being loaded has fewer pellets than are needed to completely fill amagazine pellet bore, then the bore is suitably only partially filled,with the number of pellets needed to complete that axial zone. On theother hand, if a given axial zone has more pellets than fit into asingle magazine pellet bore, then the loading station suitably fills two(or more, as needed) pellet bores of the magazine with the pellets forthat zone type.

It is also contemplated for one loading station to partially fill apellet bore of the magazine and then to have the next station downstreamalong the fuel loading conveyor belt add more pellets of a differentpellet type to fill that bore. However, this approach has thedisadvantage of making it more difficult to track the pellets of a giventype. Accordingly, in some embodiments each pellet bore of the magazineis loaded with pellets of only one type, thus simplifying tracking andrecord-keeping.

Similarly, if the total number of pellets that can be loaded into allthe bores of the pellet magazine is less than the total number ofpellets to be loaded into the fuel rod, then two or more pelletmagazines may be used to carry all the pellets for a single fuel rod.Alternatively, to enhance tracking it may be preferred to employ only asingle pellet magazine to load each fuel rod, in which case the borelength and the number of pellet bores in the magazine should be chosento be sufficient to carry all pellets for a single fuel rod.

On the other hand, if the total number of pellets to be loaded into thefuel rod is substantially smaller than the total capacity of all thebores of the pellet magazine, then some pellet bores of the magazine maybe left empty. This generally does not introduce any tracking issues.

With continuing reference to FIG. 3, after the pellet loading conveyorbelt passes the magazine through the last (i.e. furthest downstream)pellet loading station, the conveyor belt 32 then moves the filledpellet magazine 106 to a rod loading station 34. Although not shown inFIG. 3, it is contemplated to include various processing and/orrecordation or tracing sub-stations along the pellet loading conveyorbelt. For example, such sub-stations may record the pellet part number,batch, weight, rows loaded, or other information. Such sub-stations mayweigh the pellet magazine between pellet loading stations, and thechange in weight before/after passing through a given station is thenthe weight of the pellets loaded into the pellet magazine at thatstation. In some embodiments the pellet magazine may be made of atransparent or translucent material (e.g. a clear plastic material) andoptical measurements may be performed to count the number of pellets ineach pellet bore. Even if the pellet magazine is made of an opaquematerial (e.g., a metal), the slots that receive the injection finger(see FIGS. 1 and 2) provides access for such optical measurements. Ifthe pellet magazine includes an RFID tag (or serial number bar code),then one or more RFID tag reader substations (or bar code readers) maybe included to track the movement of the magazine. A gamma camera 36(diagrammatically shown in phantom by dotted lines in FIGS. 3 and 4) canalso be arranged to acquire a gamma radiation image of the filled pelletmagazine 106 at the rod loading station 34 prior to transfer of thepellets into the fuel rod. Because the pellet magazine 106 is compact,i.e., of small aspect ratio as compared with the long thin fuel rod, thegamma camera 36 can be relatively small and can be mounted in stationaryfashion with the gamma radiation image acquired without moving theimaged pellet magazine 106. By contrast, gamma camera imaging of afilled fuel rod typically entails moving either the rod or the gammacamera to scan the extensive length of the fuel rod, which can lead tovarious errors and, if imaging is acquired during movement, potentialfor motion artifacts in the acquired gamma radiation image. Othermonitoring and recordation substations are also contemplated. Theacquired tracking and recordation data are suitably stored in a trackingcomputer or other electronic tracking system (not shown).

With continuing reference to FIG. 3 and with further reference to FIG.4, after the pellet loading conveyor belt 32 passes the magazine throughthe last (i.e. furthest downstream) pellet loading station, the conveyorbelt then moves the filled pellet magazine 106 to a rod loading station34. A more detailed diagrammatic side view of the rod loading station 34is shown in FIG. 4. The magazine RFID tag (or bar code, not shown) isoptionally scanned at the fuel rod loading station 34 to providelocation and traceability information for the pellet magazine unloadingoperation. The illustrative fuel rod loading station 34 includes arotating timing belt 40 carrying one or more (illustrative two) ejectionfingers 42. An (initially) empty fuel rod 44 is aligned with the pelletbore to be unloaded using a lateral or side movement mechanism (notshown in FIG. 4 but acting to move the magazine laterally transverse tothe pellet bores, i.e. into or out of the sheet in the side view of FIG.4). Optionally, a transition element 46, e.g. a tubular adapter,facilitates coupling between the pellet bore and the fuel rod 44. FIGS.3 and 4 show only the open end of fuel rod 44 proximate to the rodloading station 34; the end distal from the rod loading station may beleft open during fuel pellet loading, or is optionally capped by an endcap to ensure the pellets cannot come out the distal end. If capped, thecap is preferably a temporary cap with air holes to avoid developing abackpressure of compressed air in the fuel rod 44 as the fuel pelletsare pushed into the fuel rod. With the fuel rod 44 and the transitionelement 46 aligned with the pellet bore currently being unloaded,rotation of the timing belt 40 moves an ejection finger 42 into the slot14 of the pellet bore 12 being unloaded and that is designed to receivethe ejection finger 42 (see FIGS. 1 and 2 showing the ejection fingerslots 14 of the pellet bores 12) and the continued rotation of thetiming belt 40 drives the ejection finger 42 from the end of the slot 14furthest from the fuel rod 44 through the length of the slot 14 so as todrive fuel pellets 48 in the pellet bore into the transition element 46.As more pellets 48 are pushed into the transition element 46, the firstpellets to enter are pushed further along through the transition element46 and then into the fuel rod 44. After all pellets in the pellet boreare driven into the transition element 46 (or furthermore into the fuelrod 44), the lateral or side movement mechanism moves another pelletbore 12 of the magazine into alignment with the transition element 46and fuel rod 44, and the process is repeated for all bores containingfuel pellets until the magazine is completely unloaded. At this point,there are still a few pellets remaining in the transition element 46. Aseparate pushing device (not shown) suitably drops down to push theseremaining pellets out of the transition element 46 and into the fuel rod44. The now-loaded fuel rod is then removed and the open end throughwhich the pellets were loaded is capped by an end cap.

It will be appreciated that, although again not shown, the rod loadingstation 34 can have various monitoring and/or tracking features, such asan RFID or bar code reader, a scale for monitoring the weight of themagazine (where the change in weight before/after unloading a pelletbore corresponds to the weight of pellets that were carried in in thatbore), the illustrative gamma camera 36, optical sensors, or so forth.

With returning focus on FIG. 3, after all the loaded pellet bores areunloaded the now-empty pellet magazine 10 ₇ is transported by a magazinereturn belt 50 back to the beginning (i.e. extreme upstream position) ofthe pellet loading conveyer belt 32 to be reused to load more pelletsinto fuel rods (diagrammatically indicated in FIG. 3 by illustrativepellet magazine 10 ₈ at the terminus of the return belt 50 and byillustrative pellet magazine 10 ₉ at the starting position on theconveyor belt 32.

Conceptually, the illustrative magazines 10 ₁, 10 ₂, 10 ₃, 10 ₄, 10 ₅,10 ₆, 10 ₇, 10 ₈, 10 ₉ can be viewed as diagrammatically illustrating asingle magazine at various different points in time along itsprocessing. Additionally or alternatively, illustrative magazines 10 ₁,10 ₂, 10 ₃, 10 ₄, 10 ₅, 10 ₆, 10 ₇, 10 ₈, 10 ₉ can be conceptuallyviewed as diagrammatically illustrating different magazines at differentpoints along the loading process. This latter view comports with anadvantage of the system, namely that a plurality of magazines can beprocessed simultaneously with each magazine being at a different pointalong the process, e.g. a magazine 10 ₂ can be being loaded at pelletloading station L2 while simultaneously a magazine 10 ₃ is being loadedat pellet loading station L3 and simultaneously the pellets stored in afully loaded magazine 10 ₆ are being transferred into a fuel rod 44 atthe rod loading station 34, and so forth.

FIGS. 1-4 are merely illustrative, and numerous variants arecontemplated. For example, the slots that receive the ejection fingercan be located on the top of the pellet magazine rather than on thebottom as illustrated, in which case the timing belt carrying theejection fingers is suitably located to engage the slots on the topsurface of the magazine. It is also contemplated to omit the slotsentirely and to employ a push rod at the rod loading station to drivethe pellets into the transition element and thence into the fuel rod. Inthis alternative embodiment, the same push rod could be extended throughthe transition element to completely push all pellets into the fuel rod.As another variant, it is contemplated to omit the transition element,and to instead incorporate a flange or other coupling element integrallyonto the ends of the pellet bores that mate with the fuel rod.

In the illustrative example, the pellet bores are open at both ends.However, it is contemplated to have the pellet bores have one end closedoff, so that each pellet bore has a single open end. In this case theejection finger engagement would be modified to insert into the slotbetween the closed end of the pellet bore and the pellet immediatelyneighboring that end. As further illustrative variant, the illustrativeconveyor belts can be replaced by other conveyance systems.

The disclosed fuel rod loading systems and methods have substantialadvantages.

The pellet magazine can be routed to any number of pellet loadingstations using common conveyance systems. This allows for complex roddesigns with multiple pellet zones (and hence complex axial compositionand/or enrichment profiles) without a significant impact on cycle timebecause the magazines are loaded in parallel. By comparison, vibratoryloading systems typically require all of the enrichment types to beavailable at the pellet loading station. The operator must load andunload trays for each zone to be loaded.

The use of a designated pellet loading station for each pellet type isan effective mechanism for isolating the different pellet types. Onlyone ²³⁵U enrichment or part number may be available at any given pelletloading station. This minimizes the likelihood of inadvertent mixing ofpellets of different types. If pellets of only one type are loaded intoany given pellet bore of the magazine, then once loaded into themagazine the pellets are effectively isolated by pellet type whenpresented to the rod loading station.

Conventional vibratory loading systems typically load twenty or morerods at the same time to increase rod loading throughput. In this case,the pellets can jump from one row to another with any processinganomaly. If such pellet crossover between simultaneously loaded rodsoccurs, then all of the involved fuel rods typically must be scrapped,together with the loaded pellets. By comparison, it is estimated thatthe disclosed magazine-based rod loading approach can achieve rod-to-rodcycle times of 30 seconds with single rod loading, thus providing highthroughput while eliminating the possibility of pellet crossover betweensimultaneously loaded rods. More generally, single rod processing isadvantageous because only one rod is affected (and likely must bescrapped) if there is an issue with the pellet loading.

While illustrative FIG. 3 includes five pellet loading stations for fivedifferent ²³⁵U enrichment levels, more (or fewer) stations can beprovided, and moreover the stations can be designated for pellets ofother types. The multi-station aspect enables loading of uranium dioxide(UO₂), burnable poison (BP) pellets, and Gadolinium pellets, among othertypes. If desired, separate magazines may be used for different pellettypes to minimize the potential for cross-contamination. The changeoverbetween pellet types is minimal.

The disclosed magazine-based pellet loading system has a smallmanufacturing floor footprint compared with other rod loading systems.The cost of the loading system is also expected to be minimal, andoperator intervention is reduced. In vibratory systems, operators handlelarge, heavy sheets of pellets multiple times during the rod loadingoperation. In contrast, the disclosed magazine-based rod loading systemrequires minimal operator handling of pellets. The potential of airbornecontamination is also expected to be substantially lower with thedisclosed magazine-based rod loading systems as compared with vibratorysystems that agitate the pellets. Ventilation can be provided in theareas where pellets are handled (e.g. the pellet loading stations andthe rod loading station), while the pellet magazines can be coveredduring transportation from station to station (e.g. along the conveyorbelts 32, 50 running between the various stations L1, L2, L3, L4, L5,34).

As already noted, magazine weight can be monitored at weigh stationsmaking it possible to obtain pellet weight information by weighing themagazine at the loading stations. Similarly, optical (or other)measurement of segment length may be performed on the pellets in apellet bore via the ejection finger slots. Optional gamma camera 36 canalso be provided to directly measure ²³⁵U enrichment levels of everypellet in the magazine (which itself is tracked by an RFID, bar code, orother tracking mechanism) thus providing detailed tracking of thecontents of the loaded fuel rod.

As yet a further advantage, low forces are exerted on the pelletscompared to other methods, and the force to push the pellets into themagazine may be measured and controlled.

In the illustrative examples, the rod loading station 34 unloads pellets48 from the pellet bores 12 directly into the fuel rod 44 (optionallyvia the transition element 46). In a variant embodiment, it iscontemplated to instead unloaded into a v-trough, or into a transparentconnector rod equal in length to the fuel rod length, so that thecomplete stack of pellets may be visually inspected prior to insertioninto the fuel rod.

The preferred embodiments have been illustrated and described.Obviously, modifications and alterations will occur to others uponreading and understanding the preceding detailed description. It isintended that the invention be construed as including all suchmodifications and alterations insofar as they come within the scope ofthe appended claims or the equivalents thereof.

We claim:
 1. A method using a plurality of pellet loading stations and anuclear fuel rod loading station, the method comprising: (i)transferring a pellet magazine to each pellet loading station of theplurality of pellet loading stations in succession in a predeterminedorder and, at each pellet loading station, loading pellets of a singletype into one or more pellet bores of the pellet magazine; and afteroperation (i) is complete, unloading the pellets from the pellet boresof the pellet magazine into a nuclear fuel rod at the nuclear fuel rodloading station in a predetermined unloading order so as to transfer anordered stack of pellets into the nuclear fuel rod.
 2. The method ofclaim 1 wherein the operation (i) includes: at a first pellet loadingstation of the plurality of pellet loading stations, loading nuclearfuel pellets with a first ²³⁵U enrichment level into one or more pelletbores of the pellet magazine; and at a second pellet loading station ofthe plurality of pellet loading stations, loading nuclear fuel pelletswith a second ²³⁵U enrichment level different from the first ²³⁵Uenrichment level into one or more pellet bores of the pellet magazine.3. The method of claim 1 wherein the operation (i) includes: a firstpellet loading station of the plurality of pellet loading stations,loading nuclear fuel pellets with ²³⁵U enrichment into one or morepellet bores of the pellet magazine; and at a second pellet loadingstation of the plurality of pellet loading stations, loading burnablepoison pellets into one or more pellet bores of the pellet magazine. 4.The method of claim 1 wherein the operation (ii) includes: unloading thepellets from the pellet bores of the pellet magazine into the nuclearfuel rod by operations including inserting an element into alongitudinal slot extending along a pellet bore of the pellet magazineand moving the inserted element along the longitudinal slot to pushpellets out of the pellet bore.
 5. The method of claim 1 furthercomprising: after completing the operation (i), acquiring a gammaradiation image of the pellet magazine.